This invention relates to secondary amines having backbones containing (1) polyether moieties and (2) hydrogen-bonding moieties and to urethane/urea prepolymers and polymers thereof and to epoxy resins cured with such polyamines. These polyamines are useful as an active hydrogen component in the reaction with a polyisocyanate to form urea/urethane polymers and are also useful as chain extenders and curing agents for epoxy resins.
In general it is known to prepare polyurethanes containing urea moieties by the reaction of a polyol and water with an isocyanate and a chain extender as disclosed in Sweeney, Reaction Injection Molding Machinery and Processes (1987). Many other types of polymers and oligomers containing urea moieties in their backbone are known materials which can be prepared in a variety of ways. The majority of such materials are prepared by the reaction of an isocyanate with an amine. The resulting products can range from simple monomers as disclosed in U.S. Pat. Nos. 3,294,749; 3,386,955; and 3,386,956, to oligomers as disclosed in U.S. Pat. Nos. 3,248,424 and 4,332,953, to soluble polymers as disclosed in U.S. Pat. No. 3,639,338, to dispersions in polyols as disclosed in German Patent 3,125,402. It is generally known that the introduction of urea moieties into a polyurea/urethane polymer improves the high temperature mechanical properties of the polymer.
Compounds or polymers containing trifunctional biuret moieties are generally produced by the reaction of a polyisocyanate with water. In such a reaction, a small number of isocyanate moieties are hydrolyzed to amino moieties by reaction with water. These amino moieties, in the presence of larger quantities of isocyanate moieties, react to form polyisocyanates containing urea moieties. Further reaction of the urea moieties with additional polyisocyanates produces polyisocyanates containing biuret moieties. These biuret-containing isocyanates have been known for many years and have been used in a variety of applications, for example as shown in U.S. Pat. Nos. 4,028,313; 4,203,875; 4,284,544; 4,289,813; 4,305,977; 4,388,245; and 4,449,591. It is generally recognized that the inclusion of trifunctional biuret moieties into a polyurea/urethane polymer produces a material having increased cross-link density.
Polyamides of polycarboxylic acid and poly(alkyleneoxy)polyamines are well-known compositions. Polyurethane coating compositions based on the reaction products of poly(propyleneoxy)polyamines with isocyanate-polyol prepolymers blocked with lactams are disclosed in JP 59/226062 (1984). Polyether polyols containing amide groups produced from partially aminated polyether polyols and adipoyl chloride or terephthaloyl chloride by reactions with isocyanates to produce urethane polymers are disclosed in DE 2,559,372 (1977). Imines of polyether polyamines are disclosed in U.S. Pat. No. 4,789,691 (1988).
It is also known to prepare isocyanate-functional prepolymers having urea moieties or biuret moieties or combinations thereof. Such isocyanate-functional prepolymers are prepared by first reacting a polyhydroxyl compound such as a polyether polyol with excess isocyanate. The resulting isocyanate-functional prepolymer is then chain-extended with reactions with polyamine or amino alcohols to produce polymers containing urethane and urea moieties in their backbones, such as shown in U.S. Pat. Nos. 3,471,449; 3,583,937; 3,627,714; 3,668,173 and 3,936,409. In some instances, the polymers contain only urea moieties in their backbones. In other cases, the polymers contain both urea and biuret moieties in their backbones. It is also known to react an isocyanate-functional prepolymer with a monofunctional amine to give polymers or oligomers which contain urea moieties near the end of the molecule as shown in U.S. Pat. No. 4,522,986.
In the polyurethanes and polyureas of the prior art containing urea and/or biuret moieties, the urea and/or biuret moieties are found to reside only in the hard segment of the resulting polyurethane or polyurea. Such polyureas/urethanes are observed to exhibit properties such as modulus, strength, hardness, toughness and solvent resistance which are less than are desired for many applications.
In the field of epoxy resins, it is also known to employ polyamines as curing agents for a wide variety of epoxy resins such as the polyglycidyl ethers of polyphenols including, for example, the epoxy novolacs and the bisphenol-A based epoxy resins. Unfortunately, these resins cured with conventional polyamines often do not have the toughness desired for many applications.
In view of such deficiencies of such prior art materials, it would be highly desirable to provide a polyurethane or polyurea having the desirable properties contributed by having urea, thiourea, dithiobiuret and/or biuret moieties without sacrificing significantly the properties of modulus, strength, hardness, toughness and solvent resistance. Further it is desirable to provide advanced epoxy resins having increased toughness.